There was a story (not military but thread related) from a student halls tower block in Manchester (UMIST, not a proper university) in the mid-70s. Co-ordinated flush, called via the stairwell, along the lines of "Trap 3, 10 seconds, now" or words to that effect. Trap 3 on 9 floors flushed simultaneously, which apparently created enough flow to lift the manhole cover in the street and forcibly remove the Chinese student sat on Trap 3, ground floor. Someone said he wasn't very happy about it.